Referring to FIG. 1, a network centralized control mode is adopted in LTE (Long Term Evolution) system, that is, both the uplink data and the downlink data of UE (user equipment) are transmitted and received under the control of a network. Communications between one UE and another UE are forwarded and controlled by the network. There is no direct communication link between two UEs, and the UE is also not allowed to transmit the uplink data spontaneously.
Referring to FIG. 2, the existing D2D (Device to Device) communication refers to direct communication between one UE and another UE through technologies of Bluetooth, Wifi (Wireless Fidelity) and the like, such communication utilizes license-free frequency band resources, and is the own behavior of users, free from the management and control of a network operator, and limited in application scenes.
Another mode is introducing a D2D technology in a mobile communication operator network. In this D2D communication mode, direct communication between one UE and another UE is allowed to a certain extent, and these direct communication links may be established under the control or assistance of a network. The basis of carrying D2D communication between one UE and another UE is discovering the close UE.
However, in the prior art, there are no technical solutions of the mutual discovery of UEs under the control of a mobile communication network.